US2568780A - Rectifier manufacturing process and products obtained thereby - Google Patents

Rectifier manufacturing process and products obtained thereby Download PDF

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Publication number
US2568780A
US2568780A US731834A US73183447A US2568780A US 2568780 A US2568780 A US 2568780A US 731834 A US731834 A US 731834A US 73183447 A US73183447 A US 73183447A US 2568780 A US2568780 A US 2568780A
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United States
Prior art keywords
selenium
cathode
electrolysis
electrolyte
gray
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Expired - Lifetime
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US731834A
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English (en)
Inventor
Hippel Arthur Von
Mortimer C Bloom
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STC PLC
Federal Telephone and Radio Corp
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Standard Telephone and Cables PLC
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Priority to US731834A priority Critical patent/US2568780A/en
Priority to CH297972D priority patent/CH297972A/fr
Priority to FR966437D priority patent/FR966437A/fr
Application granted granted Critical
Publication of US2568780A publication Critical patent/US2568780A/en
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D48/00—Individual devices not covered by groups H10D1/00 - H10D44/00
    • H10D48/01—Manufacture or treatment
    • H10D48/04—Manufacture or treatment of devices having bodies comprising selenium or tellurium in uncombined form
    • H10D48/043—Preliminary treatment of the selenium or tellurium, its application to foundation plates or the subsequent treatment of the combination
    • H10D48/0431—Application of the selenium or tellurium to the foundation plate
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/54—Electroplating: Baths therefor from solutions of metals not provided for in groups C25D3/04 - C25D3/50
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D48/00—Individual devices not covered by groups H10D1/00 - H10D44/00
    • H10D48/01—Manufacture or treatment
    • H10D48/04—Manufacture or treatment of devices having bodies comprising selenium or tellurium in uncombined form
    • H10D48/043—Preliminary treatment of the selenium or tellurium, its application to foundation plates or the subsequent treatment of the combination

Definitions

  • This invention relatesgenerally to improvements in processesfor the manufacture'of asymm'et'r-ic electrical conductors useful in rectifyinga-l't'ernating current and'in particular it is concerned with a novel 'pro'cessfor producing a new improved type of selenium rectifier. 7
  • selenium rectifi'e'rs are manufactured'byapplying to a metallic base plate pulverised amorphous selenium to which has been added afconductivit'ypromoting agent,- heating initially 'tosoften or fuse theselenium preferably under pressure thereby caus-I ing "it to distribute itself as asubstantially uniform coating on theplate and then later con- (012 204-5)f V T vertingit*cornp1etely"from theamorphous 'to' the gray or metallic variety, applying ametallic conductor "as a-*counterelectrode; and thereafter electroforming to develop the rectify-ingqual-ities of the element.
  • softe'n'ed or fused material may fail to coalesce with the result that in the finished rectifier the counterelectrode will make direct contact with the baselpla'teand-cause a short circuit.
  • This operatioln'fislurther complicated by the contraction of the volume of the selenium when the. amorphous formis convertedto' the metallic form which also'can; produce discontinuities inthefilm unlessspecial precautions aretaken.
  • the heating can cause superfi-' cialoxidation of the exposedarea of the base plate with the result that even if selenium is then applied tothis-area it will not adhere and malgesatisfactory electrical contact.
  • detection may materially and advers ,y ffe th -i eer pert e 9f; he .6 m
  • the objects of this invention include providing a new, simple, easily operated and commercially practicable process for manufacturing selenium rectifier elements, free from the disadvantages above mentioned, and. which is capable of producing rectifiers having a uniformity of electrical characteristics and an eificiency of operation to a degree hitheto unachieved in commercial production.
  • jects are achieved by directly electrolytically depositing metallic selenium upon the metallic base plate as the cathode durin'g' electrolysis of an aqueous electrolyte containing tetravalent selenium cations, preferably an aqueous solution of selenium dioxide or selenious acid. At least the initial period of this electrolysis is conducted at an elevated temperature for reasons hereinafter appearing. I'he selenium deposits obtained by practice of this new process are tenaciously adherent to the base plate and are substantially entirely composed of the metallic form of seleniumfree from the red form of the element.
  • a further advantage of this novel process for producing selenium rectifiers is that the selenium deposit is invariablyobtained as a continuous film irrespective of how thin the deposit may be. This arises from the fact that the selenium film presents resistance to .electrical current flow during the electrolysis, hence it will be obvious that any discontinuities in the film would im-- mediately, constitute foci for further deposition of the selenium.
  • rectifiers utilizing extremely thin selenium layers may be made which have a correspondingly very low resistance to current flow in the more readily conducting direction. For example, rectifiers square centimeter at 18 volts in the less readily conducting direction, both measurements having been made at room temperature.
  • An additional advantage of the process according to this invention which is of particular importance in the manufacture of selenium photocells, is that the light absorptive qualities of the selenium may be altered by adjustment of the conditions of electrolysis, for example, the color of the deposits may be varied from light gray to deep black with corresponding change in reflectivity for visible light from about at least 25% to 4% or less. This variation in appearance of the deposit is due to variation in the size and orientation of the individual crystallites which constitute the mat.
  • the size of the crystallites may be varied from sub-microscopic dimensions up to a size readily observable with the naked eye and the orientation of the individual crystallites may be .varied from the condition in which substantially all of, the crystallites are C axis oriented normally to the supporting surface to a condition in which the C axis is far from normal to this surface.
  • Figure 1 is a graph illustrating the relationship of temperature variation to the rate of transformation of amorphous selenium to nuclei of gray crystalline selenium.
  • Figure 2 is a graph indicating the relationship I of selenium dioxide concentrationin the electrolyte with the cathode efficiency for selenium deposition.
  • Figure 3 is a graph illustrating the relationship of maximum permissible current density in the electrolysis to the acid normality at difierent concentrations of selenium dioxide in the electrolyte.
  • thermodynamic concentration of the tetravalent seleniurnions in the reaction mixture will vary in the 4th power as the thermodynamic concentration of the hydrogen ion is changed and in the reciprocal third power as thermodynamic concentration of the water is altered, and in direct ratio as the thermodynamic concentration of the selenious acid is changed.
  • thermodynamic concentrationof the hydrogen ion and the thermodynamic concentration of the selenious acid are to be maintained at the highest practicable values, and the thermodynamicconcentration of water in the equilibrium mixture is to be reduced as far as possible.
  • the electrolyte pref- -'erably comprises a "highly concentrated solution lowratio of tetravalent selenium-ionstohydrogen ions, thus limiting the current denSitleS Wh-iGl1 may be used without hydrogen evolution.
  • This last condition, namely hydrogen evolutienat the cathode, is particularly undesirable :in rectifier manufacture because the bubbles of' gas are likely 'to-adhere to the cathode surface -"andinter fere with the formationota continuous ueposit.
  • the rate of formation of nuclei of the gray form passes through a maximum value at-a temperature in the neighborhood of. Cnto '1i00 C., and drops speedily on either side of this interval to relatively low values.
  • the optimum temperature range is between about 75 C. and about C. If the bath is operated at temperatures. outside this range, 1. e. temperatures at which the transformation velocity from the red into the gray form is very low, any red material initially formed stays as such for a long time.
  • the selected acid must be adapted for use in concentrations at which the desired concentration of hydrogen ions will be present in the solution and atithese'concentrations it must be free from any materialitendency to attack the base plate or theselenium deposit.
  • the metal selected for the base plate will of course be an important factor in determining the suitability of particular acids.
  • the common strong inorganic mineral acids have been found to be preferable, sulfuric acid being the most satisfactory under usual conditions, although selenic acid is also satisfactory.
  • Nitric acid althoughsatisfactory in most respects, has
  • Excellent deposits can be obtained on plati- :num',; nickel, silver, antimony, steel and other metals; and it is preferred to choose the acid to be employed with regard to the metal used as a cathode so as to prevent attack on the cathode by the acid.
  • the cathode a metal which tends to react with the acid used in the bath, special precautions 'must be taken in initiating the plating in order to prevent the acid from acting on the cathode beforethe selenium plating is started.
  • selenium coated article as used, herein embracesselenium rectifiers, and selenium photocells and objects bearinga protective coating of selenium of the type hereinabove described; by an electrodeposited selenium coating is meant a coating of the type obtained by practice of the vhereindescribed process, whether due to electrolysis or due to other phenomena occurring under the conditions of operation; and by tetravalent selenium ions is meant tetravalent selenium cations per se or a cation containing tetravalent selenium capable of discharging metallic selenium at the cathode upon electrolysis as above described.
  • electrolyte is meant a solution capable of conducting an-electric'current and of being decomposed thereby.
  • a strong acid is one that is highly dissociated to give hydrogen ions in solution even at merely moderate dilutions, for example sulfuric acid. 7
  • Example 1 An electrolyte is prepared by dissolving pure selenium dioxide in slightly more than an equal weight of pure water at room temperature, and the solution is then filtered using precautions to prevent contamination. The solution is then concentrated by heating and pure sulfuric acid is added in a quantity. such that the resultant electrolyte contains the following substances in substantially indicated proportions:
  • This electrolyte is placed in a container formed of a material inert to the electrolyte under conditions of use, erg. glass, stainless steel and the like, which is provided with a suitable protective cover for excluding contaminants and is equipped with such auxiliary apparatus as may be desired for supporting-the electrodes therein while immersed in the electrolyte.
  • the container- also is provided with auxiliary apparatus for circulating the electrolyte therein during the electrolysis and also means for permitting temperature control ofthe electrolyte, particularly for maintaining it at a preselected temperature without significant variations.
  • the electrodes used in the electrolysis are fabricated from an electrical conductor which is inert to the electrolyte under the conditions of use, e. g. platinum or the like, and are cleaned by operations conventional in the electrochemical arts beforeguse, e. gacidyyashing, electroproceeds.
  • the deposit formed initiallyon the cathode is alfilm of red selenium which is transformed very rapidly to the metallic formof selenium as the electrolysis After this electrolysis is completed, the-cathode is removed from the velectrolyte and is observed to be coated with an adherent deep black velvet-like deposit comprising microscopic Example 2.
  • Example 1 The process set forth in Example 1 is repeated with-themodification that the current density ,duringthe electrolysis ,ismaintained at 10 amperes per square foot of cathode surface for a sufficient time to produce .adeposit of equivalent thickness, i. e. forabout 2,30,1ninutes. After this electrolysisis completed, the cathode is removed from the electrolyte and is observed to be coated with anadherent deposit which does not have Examples The process set .forthin Example 1 is repeated except that-the electrolyte .maintained at a more elevated temperature, e. g. 125 C. or higher.
  • a more elevated temperature e. g. 125 C. or higher.
  • the initially deposited red film willhave developed a comparatively smallnumber of isolated nuclei of the grey form and thereafter the deposit-will form preferentially on these spots.
  • additional nuclei will form at a slow rate while the deposit becomes increasingly thicker on the spots already transformed to the grey metallic form.
  • the electrolysis must therefore be continued for a substantial period of time before the red film is transformed and the resulting structure will be one of peaks and valleys, these phenomena being increasingly manifested with increase in operating temperature. From the foregoing it will be evident that operation of the presently-invented process under these conditions requires toolong a period of time to be wholly satisfactory for commercialuse.
  • Example 1 The process set forth in Example 1 is repeated except that the electrolyte is maintained at a less elevated temperature, e. g. C., or lower.
  • a less elevated temperature e. g. C., or lower.
  • the initially deposited red film will bepunctured at spots due to the evolution of hydrogen gas bubbles and while the red film will gradually transform to grey metallic selenium, theresultant deposit will be pitted, the bits'usually extending through to the base plate, the phenomena being increasingly manifest with decrease in temperatureof the electrolysis. .From the foregoingit will be evident that operationofthe presently invented process under these conditions does not yield a satisfactory coatin'g for-use in rectifier.
  • Example 1 The process setforth in Example 1 is repeated with the modification that the electrolyte .containsno sulfuric acid. After formation of the initial red film, the resistance of the bath will increase considerably requiring considerable .volt age increases to maintain the specified current density. Further operation will be accompanied by vigorous hydrogen ,eivolutionand a .continuous adherent deposit willnot be obtained.
  • Example 6- The processas set forth in Example 1 is repeated with themodification that a chemically equiv.- alent quantity of pure orthophosphorio acid is substituted for the sulfuric acid therein, ,employed.” After formation of the initial red film, the resistance of the bath willincrease consider: ably requiring considerable voltage increases to maintain the specified current density. Further operation will be accompanied by vigorous hydrogen. evolution and a continuous adherent deposit will not .be obtained.
  • Example? The process asset forth in Example 1 is repeated with the modification thatthe electrolyte usedis composed of orthophosphoric acid saturated at a' temperatureof about -C. with selenium dioxide and following the initial electrolysis for 10 minutes at a current density of about 10 amperes per square foot of cathode surface, the electrolysis is then' continued for an additional period of about 29 minutes using a current density of about 75 amperes per square foot of cathode surface.
  • the product obtained after these operations has substantially the same appearance as that of the product obtained by fac ticeof theprocess ofExample 1.
  • Example-8 The process of Example'l i s-repeated with the modification that a" cliem-ically equivalent quantity'of selenic acid is -"s'ubstit'uted"for' the sulfuric acid therein employed.
  • the product obtained by these operations has the same acicular mat structure and properties as that obtained by practice of the process of Example 1.
  • Example 9 The process of Example 1 is repeated with the modifications that instead of a platinum cathode a cathode of pure annealed sheet nickel is used during the electrolysis and this cathode is al- 75 lowed to remain in the electrolyte for a short 11 period, say -30 seconds, prior to applications 'of the electrical potential; Apart from this difference in the metal base plate used, the product is identical With that obtained by practice of the process of Example 1..
  • Example 10 deposit of selenium is obtained and a rectifier madetherefrom will have a lower resistance in both the more readily conducting and in the less readily conducting directions.
  • Example 1 1 The process of Example ⁇ ! is repeated with the modification that the cathodeis an aluminum shape having a non-porous coating of nickel electroplated thereon; The product obtained by practice of this modified process is identical with that'obtained in the process of Example 10, except for the difference position. 7
  • An article of manufacture including an electrically conductive surface andv a substan tially continuous ssentiaLllyfnoh-porous coating upon said surface that comprises a mat substantially entirely composed of acicular microcrystallites of metallic gray selenium.
  • An article of manufacture including an electrically conductive surface and a substantially continuous, essentially non-porous coating upon said surface, dark gray to black in color and having a pile structure resembling velvet, substantially entirely comprising acicular microcrystalline gray metallic selenium.
  • An articleof manufacture includingan electrically conductive surface and a substantially continuous, essentially non-porous coating upon said surface that comprises gray crystalline metallic selenium directly electrodeposited thereon.
  • An article of manufacture including an electrically conductive surface and a substantial ly continuous, essentially. non-porous coating in the base plate com' upon said surface, dark gray to black in color,
  • An article of manufacture including an electrically conductive surface and a coating thereon, said coati g compr s g a t a i s y adherent, non-porous substantially black pilelike mat, free from discontinuities-and composed of acicular microcrystallites of metallic selenium.
  • An article of manufacture including an electrically conductive surface and a coating thereon, said coating being substantially continuous, substantially black, non-porous, tenaciously adherent to said surface and being composed of acicular gray microcrystallites of metalhc selenium directly electrodeposited upon said surface.
  • An article of manufacture including an electrically conductive surfacev and a coating thereon, said coating comprising a tenaciously adherent, non-porous substantially black pile like mat, free from discontinuities and composed of acicular micro-crystallites of metallic selenium, substantially all of the micro-crystallites being oriented with their C axes at least nearly normal to said surface.
  • An alternating electric current rectifier that comprises a substantially continuous, non-porous and tenaciously adherent layer of gray acicular micro-crystalline metallic electrodepositedv sele: nium.
  • An alternating electric current rectifier that comprises a tenaciously adherent, non-porous pile-like mat, free from discontinuities and composed of acicular micro-crystallites of metallic selenium.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
US731834A 1947-03-01 1947-03-01 Rectifier manufacturing process and products obtained thereby Expired - Lifetime US2568780A (en)

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Application Number Priority Date Filing Date Title
US731834A US2568780A (en) 1947-03-01 1947-03-01 Rectifier manufacturing process and products obtained thereby
CH297972D CH297972A (fr) 1947-03-01 1948-03-01 Procédé de fabrication d'un article métallique revêtu d'une couche de sélénium métallique et article métallique obtenu par ce procédé.
FR966437D FR966437A (fr) 1947-03-01 1948-03-01 Procédé de fabrication de redresseurs de courant électrique et produits obtenus par ce procédé

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2649410A (en) * 1948-06-10 1953-08-18 Standard Telephones Cables Ltd Electrodeposition of selenium
DE1276214B (de) * 1965-03-15 1968-08-29 Licentia Gmbh Verfahren zur Herstellung einer Selengleichrichterplatte

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1118887B (de) * 1959-04-13 1961-12-07 Licentia Gmbh Verfahren zur Herstellung von Selentrockengleichrichtern
DE1133471B (de) * 1961-08-30 1962-07-19 Licentia Gmbh Verfahren zur Herstellung von Selentrockengleichrichtern

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1743160A (en) * 1927-12-10 1930-01-14 Suddeutsche Telefonapp Kabel U Method of manufacturing alternating-current rectifiers
US2030443A (en) * 1934-03-15 1936-02-11 Western Electric Co Solid rectifying element
US2378513A (en) * 1942-01-21 1945-06-19 Union Switch & Signal Co Alternating current rectifier of the selenium type
US2414438A (en) * 1942-12-01 1947-01-21 Standard Telephones Cables Ltd Electrodeposition of selenium

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1743160A (en) * 1927-12-10 1930-01-14 Suddeutsche Telefonapp Kabel U Method of manufacturing alternating-current rectifiers
US2030443A (en) * 1934-03-15 1936-02-11 Western Electric Co Solid rectifying element
US2378513A (en) * 1942-01-21 1945-06-19 Union Switch & Signal Co Alternating current rectifier of the selenium type
US2414438A (en) * 1942-12-01 1947-01-21 Standard Telephones Cables Ltd Electrodeposition of selenium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2649410A (en) * 1948-06-10 1953-08-18 Standard Telephones Cables Ltd Electrodeposition of selenium
DE1276214B (de) * 1965-03-15 1968-08-29 Licentia Gmbh Verfahren zur Herstellung einer Selengleichrichterplatte

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CH297972A (fr) 1954-04-15
FR966437A (fr) 1950-10-10

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